1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method having a step of thermally processing a gate insulating film of a transistor.
2. Description of the Background Art
A conventional manufacturing method employs a technique of effecting heat treatment on a gate insulating film of a transistor, which is formed on a semiconductor substrate, within a hydrogen atmosphere for the purpose of recovery from process damages applied to the gate insulating film forming the transistor and for the purpose of reducing a thermal stress occurring on respective interfaces between the gate insulating film and the gate electrode and between the gate insulating film and the semiconductor substrate. This technique will be referred to as "sintering" hereinafter. A semiconductor device manufacturing method using conventional sintering will now be described with reference to FIGS. 15 to 17.
According to the semiconductor device manufacturing method using the conventional sintering, an element isolating and insulating film 111 is formed on a semiconductor substrate 110 so that element isolating regions are formed. Then, a gate insulating film 113 and a gate electrode 114 are formed on semiconductor substrate 110 in the element formation region. Subsequently, source/drain regions 112 located on the opposite sides of gate insulating film 113 and gate electrode 114 are formed at semiconductor substrate 110. Through these steps, a transistor of a field-effect type is formed.
Then, a protective insulating film 115 covering gate insulating film 113 and gate electrode 114 is formed. Thereafter, processing is performed to form an interlayer insulating film 116 covering protective insulating film 115, source/drain regions 112 and element isolating and insulating film 111. Then, contact holes reaching source/drain regions 112 are formed in interlayer insulating film 116. Thereafter, contact plugs 117 and 118 filling the contact holes are formed.
Then, tungsten interconnections 101 and 120 are formed on contact plugs 117 and 118 as well as interlayer insulating film 116. Contact plug 117 and tungsten interconnection 101 have resistance values which rise if they are thermally processed for a long time (several minutes) at a temperature exceeding 750.degree. C. Thereafter, a CVD (Chemical Vapor Deposition) method or a sputtering method is performed to form an interlayer insulating film 102 which covers tungsten interconnection 101 and is made of a silicon oxide film or a silicon nitride film.
Then, a contact hole 102a reaching tungsten interconnection 101 is formed in interlayer insulating film 102 by a lithography technique and a dry etching technique. Then, barrier metal film made of titanium nitride is formed over the surface of contact hole 102a and the upper surface of interlayer insulating film 102 by the CVD method or sputtering method.
Then, the CVD method is performed so that the concavities formed by the barrier metal film is filled, and a tungsten film is formed on the barrier metal film located over the upper surface of interlayer insulating film 102. The tungsten film is then subjected to CMP (Chemical Mechanical Polishing), dry etching or wet etching to form a tungsten plug 105 remaining only in the concavity formed by the barrier metal film.
Then, the CVD method or sputtering method is performed to form an aluminum film covering tungsten plug 105 and the barrier metal film. Then, dry etching is effected on the aluminum film and the barrier metal film after performing a lithography step so that an aluminum film 107 and a barrier metal film 106 are formed. Through the steps described above, the structure shown in FIG. 15 is completed. If necessary, sintering within a hydrogen atmosphere in a temperature range from 370.degree. C. to 430.degree. C. is effected on gate insulating film 113 in the state shown in FIG. 15 for recovering gate insulating film 113 from process damages and others so that a hillock of aluminum and a crack in the interlayer insulating film may not occur.
Thereafter, an interlayer insulating film 108 covering aluminum film 107 and barrier metal film 106 is formed. Then, the CVD method or sputtering method is performed to form an aluminum interconnection layer 109 on interlayer insulating film 108. Through the steps described above, the structure shown in FIG. 16 is completed. If necessary in the state shown in FIG. 16, sintering within a hydrogen atmosphere in a temperature range from 370.degree. C. to 430.degree. C. is likewise effected on gate insulating film 113 for recovering gate insulating film 113 from process damages so that a hillock of aluminum and a crack in the interlayer insulating film may not occur. Through the manufacturing process described above, the semiconductor device having the structure shown in FIG. 16 is completed.
Through the manufacturing process described above, the sintering within the hydrogen atmosphere is performed on the structure shown in FIG. 16. However, the temperature is low so that gate insulating film 113 cannot sufficiently recover from the process damages and others. For sufficiently recovering gate insulating film 113 from the process damages, the sintering temperature may be increased. However, such a high temperature may cause peeling (200) of barrier metal film 106, occurrence of a hillock 300 of aluminum interconnection 107 and a crack 400 in interlayer insulating film 108. This lowers the reliability of the semiconductor device. Accordingly, it is necessary to avoid peeling (200) of barrier metal film 106 as well as occurrence of hillock 300 of aluminum interconnection 107 and crack 400 in interlayer insulating film 108. For this reason, it is impossible to execute sintering within in an atmosphere at a high temperature, e.g., from 450.degree. C. to 600.degree. C., which will be referred to as a "high-temperature sintering" hereinafter, although this high-temperature sintering can sufficiently recover gate insulating film 113 from process damages and others. Consequently, it is impossible to manufacture the semiconductor device, in which gate insulating film 113 can sufficiently recover from process damages and others.